This invention relates to a method for packaging internal devices of an organic light-emitting diode (OLED), particularly for packaging the substrate of an organic electroluminescent (EL) thin-film layer and a package can together compactly.
An organic electroluminescent (EL) device is substantially an device in layer structure, wherein a thin film of the layer structure is usually formed on a vitreous or plastic substrate. The basic structure of the EL devices comprises a cathode, an anode, and an organic EL material layer interpolated between the cathode and the anode. A hole injection layer and a hole transfer layer are formed on one end of the EL material layer adjacent to the anode, and an electron injection layer and an electron transfer layer are formed on the other end of the EL material layer adjacent to the cathode so that both the holes at the anode and the electrons at the cathode can flow to reach the EL material layer to reunite each other and release energy in form of light.
Whereas the organic EL devices is a self-lighting body with high resolvability and excellent impact resistivity, it is considered a promising pixel devices for display of patterns. Besides, the organic EL devices is also featured in high brightness operable under a relatively lower working voltage and in proportional to the infused current, and by changing the material of an illuminable fluorescent"" layer of the EL devices, it is possible to display various visible colors.
In order to facilitate injection of electrons, the cathode of the organic EL devices is usually made of a low working functional material, which unfortunately easily incurs oxidation of the cathode and accordingly retardation of the devices efficiency. Moreover, the mentioned illuminable fluorescent layer, the hole and the electron injection layer, and the hole and electron transfer layer are very sensitive to wet, oxygen, and some environmental factors and are liable to become crystallized to have the organic EL material layer detached from the cathode, namely the so-called xe2x80x9cblack pointxe2x80x9d phenomenon, when they are encountered. Hence, for avoiding occurrence or constraining growth of the xe2x80x9cblack pointxe2x80x9d, inside of a conventional EL devices must be dehydrated at all possibilities, otherwise, the lifetime thereof would be greatly shortened in the case of an imperfect package.
An average package can implemented in the packaging process is a metallic can that not only costs relatively higher but also weighs heavier than other materials and is more possibly to be oxidized. In addition, the boundary to be sealed between the metallic package can and the substrate is usually not well flush and the package can must be filled in a jig one after another during the packaging process that requires more labor and time cost with poor binding quality.
Another kind of the package can is a vitreous can, which is fragile and more difficult for molding addition to those defects found in the metallic package can.
For improvements, this invention provides a method for packaging organic electroluminescent (EL) element shown in FIG. 1, wherein an organic EL devices of this invention is formed by:
forming an Indium-Tin oxide (ITO) anode layer 12 on a transparent substrate
forming an organic film 13 on the ITO anode layer 12;
forming a cathode layer 14 on the organic film 13, wherein the cathode layer 14 acts to feature as a low working function;
forming a binding layer 16 to a plastic laminated board 15 which may be preset with a waterproof and oxygen-proof segregated membrane 15a; and
packaging the organic EL devices in an ambient inert gas 17.
The primary object of this invention is to provide a method for packaging organic electroluminescent (EL) element that can avoid exposing an EL devices to ambient atmosphere. Another object of this invention is to prolong the lifetime of an organic EL devices. Yet another object of this invention is to provide a relatively simpler method for packaging an organic EL devices in high efficiency.
In order to realize above said objects, the method of this invention for packaging organic EL devices comprises:
forming a plurality of organic EL devices on a transparent substrate;
laying a plurality of binding layers on a plastic laminated board to form a plastic package laminated board;
forming a plurality of cavity domains on the plastic laminated board to serve for a plurality of package cans; and
binding a lateral face of the package can, namely a lateral face of the plastic laminated board having the binding layers, together with a lateral face of the transparent substrate having the organic EL devices, then drying and hardening the binding layers to form a packaged body by way of thermal heating or UV-curing so as to segregate the inside organic EL devices from the outside ambient atmosphere.
In this method, an active organic material is applied to form a uniform membrane on a transparent substrate, then a thin film of electrode material, usually an alloy of Mg/Ag or LiF/Al, is formed on the uniform membrane. A material of thermal-curing, thernal-plastic, or UV-curing is adopted for coating to obtain a waterproof and oxygen-resist laminated board, which is then punched or roll-pressed to become an indented board with cavity domains, wherein the indented configuration is adopted to avoid contact with the organic layers of the inside EL devices and the package cans to the electrode layer in order not to destroy the EL devices. And, in the environment of an inert gas, the package can is combined with the EL-elements resided transparent substrate to segregate the formed organic layers from the outside ambient atmosphere.
For more detailed information regarding advantages or features of this invention, at least an example of preferred embodiment will be elucidated below with reference to the annexed drawings.